The largest analysis to date of amyloid plaques in people’s brains confirms that the presence of the substance can help predict who will develop Alzheimer’s and determine who has the disease.
Two linked studies, published Tuesday in JAMA, also support the central early role in Alzheimer’s of beta amyloid, the protein that creates plaques. Data from nearly 9,500 people on five continents shows that amyloid can appear 20 to 30 years before symptoms of dementia, that the vast majority of Alzheimer’s patients have amyloid and that the ApoE4 gene, known to increase Alzheimer’s risk, greatly accelerates amyloid accumulation.
The findings also confirm that amyloid screening, by PET scan or cerebral spinal fluid test, can help identify people for clinical trials of drugs to prevent Alzheimer’s. Such screening is increasingly used in research. Experts say previous trials of anti-amyloid drugs on people with dementia failed because their brains were already too damaged or because some patients, not screened for amyloid, may not have had Alzheimer’s.
The research showed the ApoE4 gene had a bigger effect than some people expected, Dr. Ossenkoppele said. Even when people had one copy of a rarer ApoE2 gene that protects against Alzheimer’s, they were still at high risk of having amyloid if they had the ApoE4 gene.
So, ApoE4 "accelerates amyloid accumulation," but having amyloid accumulation doesn't necessarily mean that you'd have AD to go along with it.